Jawab:
1dan3 benar
Ada dua pernyataan benar

Penjelasan dengan langkah-langkah:

fungsi kuadrat f(x)
f(x) = ax²+bx+c
Melewati titik puncak (2, 9)
(xb, yb)
xb = -b/2a
2 = -b/2a
-b = 4a
b = -4a
---------------
yb = (b²-4ac)/-4a
9 = (b²-4ac)/-4a
b²-4ac = -36a
(-4a)²-4ac = -36a
16a²-4ac = -36a
4a(4a-c) = -36a
4a-c = -36a/4a
4a-c = -9
c = 4a + 9
--------------------------
D A N
Melewati titik (3, 8)
f(x) = ax²+bx+c
f(3) = 8
8 = a(3²)+b(3)+c
8 = 9a+3(-4a)+4a+9
8 = 9a-12a+4a+9
8 = a+9
a = 8-9
a = -1
--------------------------
b = -4a
b = -4(-1)
b = 4
--------------------------
c = 4a + 9
c = 4(-1)+9
c = 9-4
c = 5
--------------------------
f(x) = ax²+bx+c
f(x) = -x²+4x+5
--------------------------
Mana yang benar?
1. Memotong sumbu x di (-1, 0)?
f(x) = -x²+4x+5
f(-1) = -1²+4(-1)+5
f(-1) = -1-4+5
f(-1) = 0
BETUL
________________________
2. Memotong sumbu y di (0, 4)?
f(x) = -x²+4x+5
f(0) = -0²+4(0)+5
f(0) = 5
SALAH
________________________
3. f(5) = 0?
f(x) = -x²+4x+5
f(5) = -5²+4(5)+5
f(5) = -25+20+5
f(5) = -5+5
f(5) = 0
BETUL
________________________
4. Diskriminannya negatif?
D = b²-4ac
D = 4²-4(-1)(5)
D = 16+20
D = 36
SALAH
________________________
1dan3 benar
Ada dua pernyataan benar
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